Machine tool bit holder



Feb. 13, 1951 J. R. PROKSA 2,541,719

MACHINE TOOL BIT HOLDER Filed Aug. 21, 1946 2 Sheets-Sheet l 1; "Huh. "in... IIM M I a 9 6 Y [m/entor JOHN R. PRoKsA Feb. 13, 1951 RPRQKSA 2,541,719

MACHINE TOOL BIT HOLDER Filed Aug. 21, 1946 2 Sheets-Sheet 2 I Ii 6 Z WI 95 a J//////,

[5 F7 10 40 ,3 Z3 inventor JOHN R PRO/{5A Patented Feb. 13, 1951 UNITED STATES PATENT OFFICE 9 Claims.

This invention relates to bit holders and cutting tools adapted for use in connection with machine tools.

It is an object of my invention to provide a holder constructed to hold bits at diiferent rakes or clearances.

It is another object of my invention to provide a holder adapted to hold bits of different shapes.

A further object is to provide a bit holder adapted to securely fix a triangular bit in a plurality of operating positions.

It is also an object to provide a bit holder operative to exert pressure on a bit in the direction of cutting movement thereof.

Another object is to provide a bit holder operative to clamp a polyhedral bit without danger of fracture of any of the corner edges of the bit.

A further object is to provide a bit holder having a. pressure block which is readily adjustable to accommodate a plurality of bit shapes.

Further objects and advantages of the invention will appear as the description proceeds.

The invention will be better understood upon reference to the following description and accompanying drawings, in which:

Fig. 1 is a plan view of a cutting tool constructed in accordance with one form of my invention.

Fig. 2 is a side elevational view of the same.

Fig. 3 is a left end elevational view of the structure as seen in Fig. 2.

Fig. 4 is a sectional view taken as indicated by the line 5- in Fig. 2.

Fig. 5 is a sectional view taken as indicated by the line 5-5 in Fig. 4.

Fig. 6 is a sectional view, on an enlarged scale, taken as indicated by the line 6-6 in Fig. 1.

Fig. '7 is a view similar to Fig. 6 but shows a bit clamped at a different clearance.

Fig. 8 is a sectional view taken as indicated by the line 88 in Fig. 1.

Fig. 9 is a isometric view of the pressure block disclosed in the other figures.

Fig. 10 shows an adjustment of the holder to accommodate a rectangular bit.

Referring now more particularly to the drawings, there is shown at 20 a holder which, from outward appearances, may be of a conventional or other suitable form, with preferably an ofiset head 22 having a straight elongated socket 24 of preferably keyhole cross section. The socket 24 comprises a cylindrical portion 26 substantially more than 180 and substantially less than 360 in circumferential extent and merging with a relatively narrow channel indicated generally at 28 and adapted to be disposed below said cylindrical portion in service. A substantially oblong anvil or insert 29 is suitably secured, as by a screw 39, in the bottom of said channel and substantially spaced from said cylindrical portion. The anvil 29 has a free face 3| parallel to the plane containing the terminal elements of said cylindrical portion 26, and has in said face a pair of spaced longitudinal left and right V-grooves 32 and 34 diverging toward said cylindrical portion 26 and parallel to the axis of the socket 2t and pref erably equally spaced from the res ective sides 36 of the channel 28. If desired, the anvil 29 could be omitted and the V-grooves 32 and 34 formed in the base or bottom 38 of the channel 28. The upper margins Gil and 22 of the channel 28 diverge preferably symmetrically toward the cylindrical portion 26, the left margin 39 lying in the same plane as the left side M of the left groove 32, and the right margin 42 lying in the same plane as the right side it of the right groove 34.

A pressure block 38 having a shape substantially conforming to and rotatably slidable in the cylindrical portion 26 has a fiat longitudinal side 58 facing the channel 28, said block being loosely fitted in said cylindrical portion and being capable of adjustment toward the anvil 29 and having a transverse slot 52 in the upper part thereof between its ends 55 and 56, the bottom of said slot having a preferably truncated V-formation with a central facet 58 parallel to the side of said block and end facets til and 62 preferably inclined downward from the central facet when the central facet is horizontal, said end facets terminating at the cylindrical surface M of said block.

The holder head 22 over the socket 2 1 has a threaded hole Til therethrough communicating with the top of an intermediate part of the cylindrical portion 26 of the socket, a screw '82 being disposed in said threaded hole and having a preferably cylindrical terminal i4 substantially slidably engageable with the side walls it of the slot 52 and having a preferably flat end bearing face 18 selectively engageable with the facets 58, t0 and 62. Each of the planes of the left and right inclined walls 40 and 42 is preferably at an angle of substantially 20 to the axis of the threaded hole 16, for a purpose which will appear.

The block 48 has a second transverse slot 82 formed in a lateral part of the cylindrical surface M thereof, the head 22 having in a side thereof a threaded hole 84 registering with said second slot when said block is in any of its service positions in the socket 24. A screw 86 is disposed in the threaded hole 84 and preferably has a polygonal socket 821 for engagement by any suitable wrench, such as an Allen wrench. The screw 85 has a preferably reduced end 90 adapted to be projected into and substantially slidably engageable with the side walls 02 of the second slot 32, said slot being preferably closed at its ends 94 and being dimensioned so that, in cooperation with the screw end, it will limit rotation of the block 48 to extreme positions in which the side 50 of the block is inclined substantially 10 from its neutral position and defines a substantially equilateral triangular space with one or the other of the V-grooves 32 and 34.

Moreover, when the pressure screw I2 is backed away to permit a bit to be removed, and it is then desired to reinsert the bit to occupy a different adjustment, or to insert a different bit,

the pin end 90 of the screw 86, cooperating with the upper end 94 of the slot, will prevent the pressure block from dropping and from rotating so far as to temporarily interfere with the insertion of a bit.

The block 48 is preferably of substantially greater axial length than the socket 24 so as to project preferably rearwardly from sa d socket, a handle 98 being secured to the projecting part of the block and being engageable with the head 22 when the screws I2 and 86 are respectively alined with the associated slots 52 and 82 so as to position said slots for the reception of said screws. The side 50 of the block 48, when an equilateral triangular bit, such as the bit 98, is disposed in the socket 24 with a corner edge I of the bit disposed in one of the V-grooves 32, 34, is engageable with the face I02 of the bit opposite said corner edge, each of the end facets 60 and 62 of the slot 52 in the block 48 being inclined substantially less than to the central facet 58, and an end facet being at such t me engageable tangentially with the periphery I04 of the bearing face I8 of the screw I2, whereby, when the screw I2 is forced against said end facet, the triangular bit 98 may be engaged at all three faces thereof and the clamping force has a component directed toward that inclined surface 40, 42 which is at the same side as such end facet, and when the screw I2 is forced against the central facet 58, said s de 59 of the block is parallel to the free face 3| of the anvil 29, whereby to clamp a rectangular bit H0 (Fig. 10) therebetween.

When the periphery I04 of the screw terminal 14 is engaged with one or the other of the end facets 60, 62, the angle between the engaged facet and the face 18 of the screw is relatively small, so that, although theoretically only a point contact occurs, actually there is, due to the pressure of the screw, a small area of contact. Instead of employing three facets 58, 60 and 52, I could form the bottom of the slot 52 fiat and parallel to the face 50 of the pressure block 48, and, in such event, the angle between the face I8 of the screw 12 and one or the other end portion of such slot bottom would still be rather small, but it would be larger than the corresponding angle as shown in Figs. 6 and 7 and would result in practically apoint contact which is undesirable inasmuch as the periphery I04 of.

the screw 12 would tend to dig into and mar the end portions of the bottom of such slot.

The block 48 is so dimensioned and related to the head 22 as to afford substantial clearance I06 between the cylindrical surface 64 of the block and the cylindrical surface 26 of the keyhole socket 24, whereby the upper corner edge I08 of the triangular bit 98 adjacent the side of the bit pressed against a diverging wall 40 or 42 of I the socket will be clear of both such wall and the side of the block (Figs. 6 and 7) so that breakage at such corner edge will be avoided.

With the given angular relationships, it is evident that the top cutting face of an equilateral triangular bit clamped in my holder will have a 10 clearance below the horizontal, measured from the cutting edge, and the face at the other side of said edge will have a 20 clearance backward from the vertical, measured from said edge. The stated angular relationships are also preferred in order to adapt the holder to equilateral triangular bits, since each corner edge of the bit can be selectively used as the cutting edge. Of course other suitable angular relationships could be employed if desired. It will be observed also that the socket 24 is inclined to position the cutting end of the bit at a proper cutting angle.

It is apparent that I have provided a bit holder which is extremely simple and is fully capable of accomplishing the purposes herein explicitly set forth and implied.

Various modifications coming within the spirit of my invention may suggest themselves to those skilled in the art, and hence I do not Wish to be limited to the specific form shown or uses mentioned, except to the extent indicated in the appended claims, which are to be interpreted as broadly as the state of the art will permit.

I claim:

1. A bit holder comprising a body having a socket, a pressure block partially filling said socket and rotatably movable therein, the portion of said socket opposite said block having a pair of elongated V-grooves arranged side by side, said socket, between said block and said grooves, having inclined flat walls at an angle less than 60 to each other, said walls lying in the planes of the respective outer faces of said V-grooves, said pressure block being engageable with a side of an equilateral triangular bit when the opposite longitudinal corner of the bit is disposed selectively in either of said grooves, and means for applying pressure to force said block against the bit to clamp the bit in said socket, said pressure applying means being operative to exert pressure toward the selected inclined wall engaged with the bit, whereby to clamp the bit against the selected inclined wall.

2. A bit holder comprising a body having a socket, a pressure block having a clamping face and partially filling said socket and movable therein, the portion of said socket opposite said block being longitudinally grooved, said block being engageable with a side of a triangular bit when an adjacent side of the bit is engaged with a side of said socket and a corner of the bit is nested in said portion, and means for applying pressure to force said block against the bit to clamp the bit against said side of said socket,

said socket having a face in opposition to the clamping face of said block, said block being adjustable to locate its clamping face parallel to said face of said socket, said pressure applying means being operative to exert force on said block to clamp a rectangular bit between said faces.

3. A bit holder comprising a body having a socket, a pressure block having a clamping face and partially filling said socket and movable therein, the portion of said socket opposite said block being longitudinally grooved, said socket means comprising a screw carried by said body and having a fiat circular block-engaging surface, said block having, in the side thereof opposite the clamping face thereof, a surface at least the intermediate portion of which is parallel to the clamping face of said block, the end portions of said block surface forming an open angle slightly exceeding 180, said end portions being selectively engageable tangentially with and at a slight angle to said circular surface of said screw when a triangular bit is clamped as aforesaid in the holder, said circular surface being engageable flatwise with said intermediate portion to clamp a rectangular bit in said socket.

4. A holder for an equilateral triangular bit,

' said holder comprising a body having a socket of substantially keyhole cross-section, said socket having opposite flat walls converging from its larger portion toward its smaller portion, said smaller portion having surfaces at 60 angles to the respective walls, a pressure block manually rotatably shiftable and loosely fitted in said larger portion and having a flat side facing and adjustable toward said smaller portion, said block, on the side thereof opposite said flat side, having facets diverging toward said flat side, a screw threaded in said body and having a circular end bearing portion selectively engageable with said facets, the planes of said walls being each at an angle of substantially 20 to the axis of said screw, means for limiting rotation of said block to extreme positions in which said flat side of said block is inclined substantially from its neutral position and defines with one or the other wall and associated surface an equilateral triangular space, said flat side of said block, when an equilateral triangular bit is disposed in said socket with a longitudinal corner of said bit nested with one of said walls and the associated surface, being engageable with the face of the bit opposite said corner, each of said facets being inclined less than 10 to said flat side of said block, one facet being at such time engageable tangentially by said bearing portion of said screw, whereby, when said screw is forced against said one facet, the triangular bit is engaged at all three faces thereof and the clamping force is directed toward that wall which is adjacent said one facet.

5. A holder for an equilateral triangular bit, said holder comprising a body having a socket iii of substantially keyhole cross-section, said socket having opposite fiat walls converging from the larger portion of said socket toward the smaller portion of said socket, said smaller portion having surfaces at 60 angles to the respective walls.

6. A holder for an equilateral triangular bit, said holder comprising a body having a socket of substantially keyhole cross-section, said socket having opposite fiat walls converging from the larger portion of said socket toward the smaller portion of said socket, said smaller portion having surfaces at 60 angles to the respective walls, and a screw threaded in said body and engageable with a pressure block to clamp a triangular bit in said socket, the planes of said walls being each at an angle of substantially 20 to the axis of said screw.

7. A bit holder comprising a body having a socket with opposite relatively acutely inclined flat walls, a pressure block having a clamping face and partially filling said socket and rotatably movable therein, said block being rotatable to locate its clamping face at a predetermined angle to selectively either of said walls to co-operate with the selected wall in accommodating twoadjacent faces of a triangular bit, and means for applying pressure to force said block against the bit to clamp the bit in said socket against the selected wall, said socket having a pair of V-grooves to selectively nest the corner of the bit opposite the face of the bit engaged by said block.

8. In a bit holder, a pressure block having a bit clamping face and three facets in the side thereof opposite said clamping face, the intermediate facet being parallel to said clamping face and each end facet being inclined at an angle of about 10 to said clamping face.

9. In a bit holder, a pressure block having at one side a bit clamping face and at the opposite side a pair of oppositely inclined facets, for selectively receiving a pressure-applying member, each facet of said pair being inclined at an angle of about 10 to said clamping face.

- JOHN R. PROKSA.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,111,181 Rikof Sept. 22, 1914 1,387,417 Lennon Aug. 9, 1921 FOREIGN PATENTS Number Country Date 2,904 Great Britain Feb. 22, 1890 460,156 Germany May 19, 1926 520,440 Great Britain Apr, 24, 1940 

